<div class="_1l1MA">Let's only consider the cases where <code>i < j</code>, as the problem is symmetric.</div>

<div class="_1l1MA">For an index <code>j</code>, we are interested in an index <code>i</code> in the range <code>[0, j - x]</code> that minimizes <code>abs(nums[i] - nums[j])</code>.</div>

<div class="_1l1MA">For every index <code>j</code>, while going from left to right, add <code>nums[j - x]</code> to a set (C++ set, Java TreeSet, and Python sorted set).</div>

<div class="_1l1MA">After inserting <code>nums[j - x]</code>, we can calculate the closest value to <code>nums[j]</code> in the set using binary search and store the absolute difference. In C++, we can achieve this by using lower_bound and/or upper_bound.</div>

<div class="_1l1MA">Calculate the minimum absolute difference among all indices.</div>